1. Field of the Invention
The present invention relates to a compressor assembly for use in an air conditioning system, and particularly to a compressor assembly for use in an automotive air conditioning system, and to features for separating oil and compressible working fluid within compressor assemblies.
2. Description of the Related Art
Compressor assemblies for automotive air conditioning systems are well-known in the art. A compressible working fluid such as a refrigerant gas is received into the compressor assembly housing at a suction pressure and discharged therefrom at a relatively higher discharge pressure. In automotive air conditioning systems, the compressor assembly typically has a drive shaft whose rotation axis is generally horizontal and that is driven by the engine crankshaft through a drive belt coupled to the engine crankshaft pulley, which serves as a rotative power source. The compressor drive shaft is coupled to a compression mechanism within the compressor housing. The compression mechanism of a scroll-type compressor assembly, for example, has an orbital scroll member coupled to the drive shaft and a nonorbital scroll member with which it is operably engaged. The orbital scroll member is driven in a generally circular orbit about the drive shaft rotation axis relative to the nonorbital scroll member.
In a scroll-type compressor assembly, the orbital scroll member includes a plate with a flat surface that is perpendicular to the rotation axis and an involute wrap integral with the plate and extending out from the flat surface. A cooperating nonorbital scroll member includes a plate with a flat surface that is parallel to the flat surface of the orbital scroll member, and an involute wrap integral with its plate that extends from its flat surface. The wraps and flat surfaces of the orbital and nonorbital scroll members cooperate to form fluid pockets which are bound by adjacent surfaces of the intermeshed wraps. These boundaries are established by line contacts between the intermeshed wraps, and contact between the axial tips of the intermeshed wraps and the flat surfaces of the scroll plates against which the wrap tips are slidably engaged. An example of a prior such scroll compressor assembly is described in U.S. Pat. No. 5,346,376 (Bookbinder et al.) issued Sep. 13, 1994, the disclosure of which is expressly incorporated herein by reference.
The working fluid at substantially suction pressure, and in which typically an amount of substantially incompressible lubricating oil is entrained, is received in a compression mechanism inlet between the scroll members, at a radially outward location. The received fluid/oil admixture is captured within the fluid pockets defined by the interengaged scroll wraps as the orbital scroll member moves about the shaft rotation axis relative to the nonorbital scroll member. The entrained oil lubricates and cools the interengaged scroll members. A seal is normally provided in a groove provided in the axial tip of each scroll wrap, to seal between the wrap and the flat surface of the adjacent scroll member plate against which it slides. The axial tip seals are provided to accommodate thermal expansion of the scroll members.
During operation, as the orbital scroll member is driven by the shaft, the contact lines and the fluid pockets defined between the intermeshed wraps move along the surfaces of the wraps toward the centers of the cooperating scroll members. The fluid pockets become smaller in volume as they move along the wraps toward the centers of the scroll members, and the working fluid in the pockets is compressed. Thus, the fluid pockets define fluid compression chambers in which the pressure of the contained fluid is raised from substantially suction pressure to a relatively higher, substantially discharge pressure. A fluid discharge aperture is provided near the center of the nonorbital scroll member, providing a passage through which the compressed fluid and oil mixture is expelled from the compression mechanism at substantially discharge pressure. The interengaged orbital and nonorbital scroll members thus define the compression mechanism.
Excess oil entrained in the refrigerant fluid collects on surfaces of heat exchangers in the refrigerant system, impairing system performance. It is therefore desirable that oil be retained within the compressor assembly for lubricating and cooling the compression mechanism and other moving parts within the compressor housing, rather than circulate with the working fluid through the remainder of the refrigeration system.
Oil separator apparatuses external to the compressor assembly are known which separate oil from compressed refrigerant fluid adjacently downstream of the compressor assembly in the refrigerant system, with the separated oil directed to a point adjacently upstream of the compressor assembly in the refrigerant system. The separated oil thus bypasses the heat exchangers of the system, through which is directed the working fluid from which the bypassing oil has been separated. Shortcomings of such external oil separation apparatuses include their attendant packaging requirements, additional costs, and an increased number of fluid joints at which external leaks could occur.
It would be beneficial if entrained lubricating oil were separated from the compressed fluid prior to the fluid's being exhausted from the compressor housing, and retained within the compressor housing. Such an improvement would promote enhanced heat exchanger performance and reduce the overall amount of oil necessary in the refrigerant system, while avoiding the shortcomings of external oil separation apparatuses.